Training machines have been provided in the market for lifting weights vertically as resisting against the gravity to develop the muscles. Such a training machine basically comprises a base placed on the floor, a movable member arranged movable in response to the movement of the body of an exerciser, and a load exerting means for exerting a load to control the movement of the movable member. The load exerting means includes weights provided for movement vertically along guide posts and connecting wires connecting between the weights and the movable member. (See Japanese Patent Laid-open Publication (Heisei) 6-7475).
In action of the training machine, the movable member is moved to a target position by an exerciser contracting its muscles for physical training. As the movable member is moved, it causes the weights to lift up via the connecting wires as resisting against the gravity. The weights in turn provide a load to control the movement of the movable member. When the movable member has been moved to the target position by the exerciser contracting its muscles, the weights reach at a corresponding uppermost point. This is followed by the exerciser relaxing the muscles so that the movable member returns back to its original position. As the movable member is being moved back towards the original position, its sustaining the weights connected by the connecting wires lift down due to the effect of their gravity. The muscles are contracted until the movable member reaches at its target position and then relaxed with the weights pulling the movable member up to the original position. As the muscles repeat the contracting and relaxing action for the training, they can be built up through their exhaustion and stimulation.
However, the training machine has two major drawbacks, which are based on the use of weights. Firstly, when the muscles has been contracted to drive the movable member to the target position, their behavior is at the most contracted state or in the other words, the most stimulated state. As the muscles are relaxed to move back the movable member from the target position to the original position, they allow the weights to shift from the upward movement to the downward movement. In case that the weight are lifted up by a force greater than their gravity to moved the movable member, they may pop up at the uppermost point (upon the timing of shift from the upward movement to the downward movement). The pop up of the weights will thus interrupt the training action of the movable member and provide no load to the exerciser. When the exerciser receives no load from the weights at the most contracted state of its muscles (at the uppermost point of the weights), its muscles will abruptly be released from the maximum tension. As the muscles relax unintentionally, their stimulation will be declined hence permitting no development of the muscles.
Secondly, when the weights are lifted up, they resist against their gravity and thus provide the exerciser with a load which becomes greater when the speed of the training movement is increased. When the weights are lifted down, their gravity undergoes the downward movement. As the speed of its training movement becomes closer to the speed of the gravity, the exerciser receives a less load from the weights and their muscles will be less susceptible to the load. Accordingly, the muscles can remain highly responsive to the load during the upward movement of the weights but blunt during the downward movement of the weight.
It is hence essential for avoiding the abrupt relaxation of the muscles at the timing of shift from the upward movement to the downward movement of the weights to drive the movable member (or the weights) with a force substantially equal to the gravity of the weights. It is also necessary for inhibiting the relaxation of the muscles during the downward movement of the weights to drive the movable member at a speed lower than the downward movement. Most of the existing training books recommend that the training action should be conducted as at moderate speeds as possible. This however requires every exerciser to carefully control the speed for driving the movable member or the upward and downward movement of the weights during the training action. As a result, the exerciser has to concentrate its attention on the speed and will thus suffer from a mental stress. It is particularly troublesome for a beginner to exercise with control of the movement.
It is hence an object of the present invention to provide a training machine which can eliminate any pop up movement of the weights at the timing of shift from the upward movement to the downward movement even when the weights are lifted up with a force greater than their gravity.